1. Field of the Invention
The present invention relates in general to a feedback compensating apparatus used with a controller for a working machine (e.g., a metal working machine such as a grinding machine), which apparatus is adapted to adjust the working condition of the working machine by feeding back to the controller a compensating signal or data obtained during and/or after a working operation on the workpiece, so that the controller controls the working machine so as to improve the dimensional accuracy of the workpiece processed by the machine. More particularly, the present invention is concerned with techniques for improving the accuracy of adjustment of the working condition by the compensating apparatus.
2. Discussion of the Prior Art
For assuring high dimensional accuracy of processed portions of a workpiece after the workpiece is machined, ground or otherwise processed, there are available various feedback control methods such as an in-process control method, a post-process control method, and a hybrid control method. These control methods are practiced, for example, to finish inner cylindrical surfaces of cylinder bores formed in cylinder blocks of an engine of a motor vehicle, or outer cylindrical surfaces of a crankshaft of such engine, with high precision, so that the dimension such as the inside diameter of the finished cylinder bores or outside diameter of ground journals of the crankshaft is as close to the nominal value as possible.
The in-process control employs an in-process measuring device for measuring the dimension of the working portion of the workpiece during a working operation on the workpiece, so that the working operation is terminated when the measured dimension coincides with the nominal value.
Usually, the in-process control is based on an assumption that the desired or nominal dimension is obtained when the actually measured dimension reaches a reference value corresponding to the nominal dimension. To this end, the dimension of the working portion of the workpiece is continuously measured, and the measured dimension is compared with the reference value, to determine the moment when the actually measured dimension becomes equal to the reference value.
The post-process control employs a post-process measuring device for measuring the dimension of the working portion of the workpiece after the working portion has been processed or finished. A difference of the actually measured dimension from the nominal value, namely, a dimensional error of the finished workpiece is fed back to the controller for the working machine, so that the working data such as numerical control data (NC data) subsequently used by the machine for effecting the working operation on the following workpiece or workpieces are suitably adjusted so as to eliminate or reduce the dimensional error.
The post-process measuring device does not necessarily acts on the workpiece or its working portion immediately after the appropriate working operation, but may operate in a mode in which the measurement is effected a given length of time after the working operation, during which the other working portions or other workpieces are machined or otherwise processed.
The hybrid control, which is a combination of the in-process and post-process control methods, is adapted to feed back the dimensional error of the processed workpieces obtained by the measurement by the post-process measuring device, to compensate the reference value used in the in-process control, for zeroing the post-process dimensional error.
However, the known control methods indicated above and the apparatus to practice these known methods suffer from a problem that the control logics, rules and programs used in the known systems do not permit sufficiently high accuracy of adjustment of the working condition of the working machine. One presumed reason for the insufficient accuracy in the prior art lies in the mere use of the dimensional error per se to adjust the working condition, whereas various other factors or parameters affect the actual dimensions of the working portions of the workpieces and should be taken into account for improved accuracy of compensation of the working condition to eliminate the dimensional error.
It is therefore a first object of the present invention to provide a feedback compensating apparatus for use with machine control means of a working system, which apparatus assures improved accuracy of adjustment of the working condition of the working machine of the system, with suitable factors taken into account to determine a compensating signal to adjust the working condition.
It is a second object of the present invention to provide a method of processing the workpiece with high precision, while adjusting the working condition of the working machine, with suitable factors taken into account so as to assure improved dimensional accuracy of the processed workpiece.
The above first object may be achieved according to a first aspect of this invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for performing a working operation on each of at least one working portion of each of a plurality of workpieces, to process each working portion as desired, such that working operations on the plurality of the workpieces take place successively one after another, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of the working portions of the workpieces processed or under processing by the working machine, the feedback compensating apparatus being used with the machine control means and the measuring device, the apparatus comprising: (i) data obtaining means for obtaining dimensional data on the basis of outputs of the measuring device during at least one of a first period and a second period following the first period, the working operation on each working portion being performed during the first period, the dimensional data including a dimensional error of the working portions of the workpieces, and a variable indicative of a tendency of change in the dimensional error of the workpieces; and (ii) compensating means for determining a compensating signal as the extraneous signal on the basis of the dimensional data, and applying the compensating signal to the machine control means, to adjust the working condition of the working machine.
In the feedback compensating apparatus of the present invention constructed as described above, the working condition of the machine is adjusted on the basis of not only the dimensional error of the processed working portions of the workpieces, but also the tendency of change in the dimensional error. The use of a variable indicative of the actual change in the dimensional error in addition to the dimensional error makes it possible to more accurately estimate the actual working condition of the machine, than the use of only the dimensional error. Thus, the present compensating apparatus permits improved adequacy of the compensating signal used to adjust the working condition for enhanced dimensional accuracy of the processed working portions of the workpieces.
The principle of the present invention described above is applicable to various types and modes of operation of a working system, which include (1) a configuration wherein a plurality of workpieces each having only one working portion are successively processed one after another by a single working tool, (2) a configuration wherein a plurality of workpieces each having a plurality of working portions are successively processed, such that the different working portions on each workpiece are successively processed by a single working tool, and (3) a configuration wherein a plurality of workpieces each having a plurality of working portions are successively processed, such that the different working portions on each workpiece are processed by respective working tools, either successively or simultaneously.
In the third configuration indicated at (3) above, the present invention is applicable to all the working portions of each workpiece, such that the compensating signal is determined for each one of the different working portions of the same workpiece. Where the working portions of each workpiece have substantially the same shape and size, however, the dimensional data may be obtained for only a selected one or ones of the working portions, but not for all the working portions. In this case, the compensating signals for the non-selected working portions are determined by utilizing the compensating signal or signals actually determined based on the dimensional data on the selected working portions.
The term xe2x80x9cworking portionxe2x80x9d used herein may be a cylindrical surface of the workpiece which has the same diameter over the entire axial length, or each of a plurality of coaxial cylindrical surfaces of the workpiece which have different diameters at respective axial positions. In the former case, the cylindrical surface as the working portion has only one xe2x80x9cdimensionxe2x80x9d within the meaning of the present invention. In the latter case, each of the cylindrical surfaces having different diameters has the xe2x80x9cdimensionxe2x80x9d.
The term xe2x80x9cto adjust the working conditionxe2x80x9d used herein is interpreted to mean any adjustment which eventually causes a change in the working condition of the machine, and which may be a direct adjustment of a specific parameter that determines the working condition, or an indirect adjustment of a parameter whose change will result in a change in the working condition.
The term xe2x80x9ccompensating signalxe2x80x9d used herein is interpreted to mean a signal to be fed from the compensating means to the machine control means, which signal may be a signal indicative of an amount of adjustment of the currently established working condition of the machine, or a signal indicating that the actually measured dimensional error of the workpiece or the actually obtained tendency of change in the dimensional error is not held within a tolerable range. In the former case, the compensating means may be adapted to determine a compensating value on the basis of at least the dimensional error and the variable indicative of the tendency of change in the dimensional error, and apply to the machine control means the compensating signal indicative of the compensating value, so that the working condition of the machine is adjusted according to the compensating value. In the latter case, the compensating means may be adapted to determine on the basis of the dimensional error and the variable, whether the dimensional error of the workpiece is held within the tolerable range or not, and further adapted to apply the compensating signal to the machine control means when the dimensional error is outside the tolerable range, so that the working condition is adjusted by a predetermined amount according to the compensating signal. In this case, the compensating means may be arranged to produce the compensating signal each time the excessive dimensional error of the workpiece is detected, or when the excessive dimensional error is detected two or more successive times. Alternatively, the machine control means may be adapted to adjust the working condition each time the compensating signal is received from the compensating means, or when the two or more successive compensating signals are received.
According to one form of the present invention, the measuring device includes a post-process measuring device for measuring the actual dimensions of the processed working portions of the workpieces during the second period, and the working system further includes an in-process measuring device for measuring the actual dimensions of the working portions during the first period. Further, the data obtaining means obtains, as the dimensional error, differences between the actual dimensions of the processed working portions measured by the post-process measuring device and a nominal value of the working portions. The data obtaining means further obtains a variable indicative of a tendency of change in the differences. The compensating means determines the compensating signal on the basis of the differences and the variable indicative of the tendency of change in the differences, and applies the compensating signal to the machine control means so as to adjust a reference value which is set in the machine control means as the working condition, so that an output of the in-process measuring device is compared with the reference value as adjusted according to the compensating signal. The working operations of the machine are terminated when the output of the in-process measuring device coincides with the adjusted reference value.
The above arrangement is adapted to effect a semi-hybrid control of the working condition of the machine, wherein the dimensional data on processed working portions or workpieces are used to adjust the working condition of the machine for subsequently processing the following working portions or the following workpieces. In this semi-hybrid control, the in-process measuring device temporarily functions as if it were a post-process measuring device.
However, the principle of the present invention may be embodied as a feedback compensating apparatus adapted to effect an in-process control of the working condition of the machine. In this case, the measuring device is an in-process measuring device, and the data obtaining means obtains the dimensional error in the form of differences between the actual dimensions of the individual working portions measured by the in-process measuring device and the nominal dimension of the working portions, while the working operation is in progress on each working portion. The data obtaining means also obtains the tendency of change in the obtained dimensional error (above-indicated differences) in the process of the working operation on each working portion. The compensating means determines the compensating signal on the basis of the dimensional error and the tendency of change in the dimensional error, so that the working condition (e.g., a feeding amount or rate of the working tool or tools) of the machine is adjusted during the working operation on the working portion whose dimensional data are obtained based on the output of the in-process measuring device.
The present invention may also be embodied as a feedback compensating apparatus adapted to effect a post-process control of the working condition of the machine. In this case, the measuring device is a post-process measuring device for measuring the dimensions of the processed working portions of the workpieces, and the data obtaining means obtains the dimensional error and tendency of change in the dimensional error of the processed working portions, on the basis of the output of the post-process measuring device. The compensating means determines the compensating signal based on the dimensional error and the tendency of change, so that the working condition of the machine in the form of numerical data, for example, is adjusted according to the compensating signal fed back from the compensating means.
According to another form of the present invention, the compensating means determines the compensating signal in the form of successive compensating values representative of respective amounts of adjustment of the working condition, on the basis of the dimensional data on the working portions successively processed by the machine. In this form of the invention, the compensating means comprises determining means for determining the successive compensating values such that a present one of the successive compensating values is determined on the basis of the dimensional data currently obtained by the data obtaining means, and at least one preceding compensating value of the successive compensating values which precedes the present one compensating value. For instance, the determining means may be adapted to determine a present provisional compensating value as the present one of the successive compensating values on the basis of the dimensional error and the variable indicative of the tendency of change in the dimensional error, and adjust the present provisional compensating value into a present final compensating value such that the present final compensating value lies on a line which is determined by the present provisional compensating value and a plurality of preceding provisional compensating values which precede the present provisional compensating value, the line assuring a gradual change in the amounts of adjustment of the working condition.
The above form of the invention is based on a general tendency that the dimensional error of the processed working portions of the different workpieces or the same workpiece changes gradually without a sudden or abrupt change, as the number of the workpieces increases or as the working operation on the same workpiece progresses. To improve the dimensional accuracy of the processed working portions, therefore, it is desirable that the compensating value which determines the amount of adjustment of the working condition of the machine gradually changes with a gradual change in the dimensional error. In this respect, the present compensating value is preferably determined on the basis of not only the dimensional data (dimensional error and the tendency of its change) but also at least one preceding compensating value which was used previously to adjust the working condition. The present arrangement permits increased accuracy of adjustment of the working condition by the feedback compensating apparatus.
While the present final compensating value described above is determined by adjusting the present provisional compensating value based on the preceding compensating values (preceding provisional compensating values), the present final compensating value may be obtained by adjusting the present provisional compensating value on the basis of the preceding final compensating values. Alternatively, the present final compensating value may be obtained directly on the basis of the dimensional data and at least one preceding final compensating value.
According to a further form of the invention described above, the data obtaining means obtains on the basis of the outputs of the measuring device, the dimensional error, a first variable indicative of the tendency of change in the dimensional error, and a second variable indicative of a tendency of change in the first variable, during at least one of the first and second periods. This arrangement permits more adequate adjustment of the working condition, owing to the additional use of the second variable which accurately reflects an actual change in the dimensions of the processed workpieces.
The second object indicated above may be achieved also according to the first aspect of this invention, which provides a method of processing at least one working portion provided on each of a plurality of workpieces, such that the workpieces are successively processed one after another by a working machine, comprising the steps of: (i) obtaining dimensional data including a dimensional error of the processed working portions of the workpieces, and a variable indicative of a tendency of change in the dimensional error of the workpieces, during at least one of a first period during which a working operation on each of the at least one working portion is performed and a second period following the first period; and (ii) feeding back the dimensional data to the working machine, to adjust a working condition of the machine on the basis of the dimensional data, for subsequent working operations on the working portions of the workpieces according to the adjusted working condition.
The first object may also be achieved according to a second aspect of the present invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for successively processing a plurality of workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, the feedback compensating apparatus being used with the machine control means and the measuring device, the apparatus comprising (i) data obtaining means for obtaining dimensional data on the basis of outputs of the measuring device, and (ii) compensating means for determining a compensating signal as the extraneous signal on the basis of the dimensional data. The dimensional data include a dimensional error of the processed workpieces, and a variable indicative of a tendency of change in the dimensional error of the workpieces. The data obtaining means obtains a present value of an estimated dimension of the working portions of the workpieces on the basis of a predetermined first number of successive measured values represented by the outputs of the measuring device, when each of the workpieces is measured by the measuring device, the predetermined number of successive measured values consisting of a currently measured value currently obtained by the measuring device and at least one measured value which precedes the currently measured value. The data obtaining means further obtains a present dimensional error value which is a difference of the present value of the estimated dimension from a nominal dimension of the working portion of each workpiece. The data obtaining means obtains a present value of the variable indicative of the tendency of change in the dimensional error, on the basis of a predetermined second number of successive dimensional error values, when the present dimensional error value is obtained, the predetermined number of successive dimensional error values consisting of the present dimensional error value and at least one error value which precedes the present dimensional error value. The data obtaining means includes at least one of dimension estimating means and variable obtaining means. The dimension estimating means obtains the present value of the estimated dimension in a standard manner when the number of the successive measured values currently available is not smaller than the predetermined first number, and in a special manner different from the standard manner, when the number of the successive measured values currently available is smaller than the predetermined first number. The variable obtaining means obtains the present value of the variable in a standard manner when the number of the successive dimensional error values currently available is not smaller than the predetermined second number, and in a special manner different from the standard manner for the variable, when the number of the successive dimensional error values currently available is smaller than the predetermined second number. The compensating means applies the compensating signal to the machine control means, to adjust the working condition of the working machine.
In the feedback compensating apparatus constructed according to the second aspect of this invention described above, the data obtaining means includes the dimension estimating means and/or the variable obtaining means which operate as described above. Namely, when the number of the successive measured values of the workpieces currently available to obtain the present value of the estimated dimension is smaller than the predetermined number, the dimension estimating means operates in a special mode in which the present value of the estimated dimension is obtained in the special manner different from the standard manner practiced when the number of the currently available successive measured values is equal to or larger than the predetermined number. When the number of the successive dimensional error values currently available to obtain the present value of the variable indicative of the tendency of change in the dimensional error is smaller than the predetermined number, the variable obtaining means operates in a special mode in which the present value of the variable is obtained in the special manner different from the standard manner practiced when the number of the currently available successive dimensional error values is equal to or larger than the predetermined number.
According to the above arrangement, the estimated dimension of the processed workpieces can be obtained even when the number of the currently available successive measured values is smaller than the required number, if the the data obtaining means is provided with the dimension estimating means. Similarly, the variable indicated above can be obtained even when the number of the currently available successive dimensional error values is smaller than the required number, if the data obtaining means is provided with the variable obtaining means. Accordingly, the provision of the dimension estimating means and/or the variable obtaining means effectively reduces or eliminates a time during which it is impossible to determine the compensating signal on the basis of the dimensional data, due to shortage of the currently available data on the measured dimensions of the workpieces and the variable indicative of the tendency of change in the dimensional error.
The above second object may also be achieved also according to the second aspect of the present invention, which provides a method of processing a plurality of workpieces by a working system including (a) a working machine for successively processing the plurality of workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, the method being characterized by comprising: (i) a step of obtaining dimensional data on the basis of outputs of the measuring device, the dimensional data including a dimensional error of the processed workpieces, and a variable indicative of a tendency of change in the dimensional error of the workpieces, the step of obtaining dimensional data including the sub-steps of (a) obtaining a present value of an estimated dimension of the working portions of the workpieces on the basis of a predetermined first number of successive measured values represented by the outputs of the measuring device, when each of the workpieces is measured by the measuring device, the predetermined number of successive measured values consisting of a currently measured value currently obtained by the measuring device and at least one measured value which precedes the currently measured value, (b) obtaining a present dimensional error value which is a difference of the present value of the estimated dimension from a nominal dimension of the working portion of the each workpiece, and (c) obtaining a present value of the variable, on the basis of a predetermined second number (L) of successive dimensional error values, when the present dimensional error value is obtained, the predetermined number of successive dimensional error values consisting of the present dimensional error value and at least one error value which precedes the present dimensional error value; and (ii) a step of determining a compensating signal as the extraneous signal on the basis of the present value of the estimated dimension and the present value of the variable, and applying the compensating signal to the machine control means, to adjust the working condition of the working machine, and wherein the step of obtaining dimensional data is characterized by comprising at least one of two features (d) and (e), the feature (d) consisting in obtaining the present value of the estimated dimension in a standard manner when the number of the successive measured values currently available is not smaller than the predetermined first number, and in a special manner different from the standard manner, when the number of the successive measured values currently available is smaller than the predetermined first number, the feature (e) consisting in obtaining the present value of the variable in a standard manner when the number of the successive dimensional error values currently available is not smaller than the predetermined second number, and in a special manner different from the standard manner for said variable, when the number of said successive dimensional error values currently available is smaller than said predetermined second number.
The first object may also be attained according to a third aspect of this invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for successively processing a plurality of workpieces one after another, each of the workpieces having a plurality of working portions in the form of a plurality of coaxial outer cylindrical surfaces arranged in an axial direction thereof, the working machine including an array of working tools which correspond to the plurality of working portions, respectively, the array of working tools being moved relative to each workpiece to simultaneously process the working portions, (b) an in-process measuring device having two in-process measuring heads for measuring diameter values of respective two end working portions of the plurality of working portions, during a working operation of the machine on each workpiece, the two end working portions being located near opposite axial ends of each workpiece, (c) a post-process measuring device for measuring diameter values of the plurality of working portions, respectively, after each workpiece is processed by the machine, and (d) machine control means for controlling the machine such that an operating angle of the array of working tools relative to each workpiece is adjusted and the working operation of the machine on each workpiece is terminated, on the basis of the diameter values of the two end working portions measured by the in-process measuring heads, in relation to two reference values set for the two end working portions, respectively, the feedback compensating apparatus being used with the post-process measuring device and the machine control means, the apparatus comprising: (i) determining means for determining two compensating values for adjusting the two reference values, on the basis of the diameter values of all of the plurality of working portions of each workpiece measured by the post-process measuring device; and (ii) applying means for applying the two compensating values to the machine control means.
In the feedback compensating apparatus constructed as described above according to the third aspect of this invention, the compensating values for adjusting the reference values of the two end working portions of the workpiece are determined on the basis of not only the diameter values of these two end working portions measured by the post-process measuring device, but also the measured diameter values of the other working portions. This arrangement permits the reference values used to control the machine to be adequately adjusted so as to minimize the dimensional error of the processed working portions of the workpieces, in view of the diameter values of all the working portions actually measured by the post-process measuring device.
The term xe2x80x9ca plurality of coaxial outer cylindrical surfacesxe2x80x9d as the working portions of each workpiece is interpreted to include not only coaxial cylindrical portions of the workpiece which have the same outside diameter, but also coaxial cylindrical portions thereof which have different outside diameters.
Further, the term xe2x80x9ctwo end working portionsxe2x80x9d of each workpiece is interpreted to mean not only the two axially outermost outer cylindrical surfaces nearest to the opposite axial ends of the workpiece, but also two outer cylindrical surfaces which are axially inside the axially outermost outer cylindrical surfaces and are relatively near the opposite axial ends of the workpiece.
Each of the xe2x80x9ctwo reference values set for the two end working portionsxe2x80x9d is interpreted to include at least a reference value indicative of an amount of movement of the array of working tools relative to the workpiece, which amount is required to establish a nominal outside diameter of the corresponding end working portion. That is, the reference value for each of the two end working portions should include a reference value indicative of a time at which the working operation on the corresponding end working portion is terminated, and may include at least one reference value corresponding to an outside diameter of the end working portion which is larger than the nominal outside diameter.
The phrase xe2x80x9can operating angle of the array of working tools relative to each workpiece is adjusted and the working operation of the machine on each workpiece is terminated, on the basis of the diameter values of the two end working portions measured by the in-process measuring heads, in relation to two reference values set for the two end working portions, respectivelyxe2x80x9d may be interpreted to mean the following two modes of control of the machine by the machine control means, for example.
In one mode of control of the machine, when one of the two reference values set for the respective two end working portions is reached before the other reference value, the operating angle is adjusted based on a difference between the above-indicated other reference value and a value corresponding to the outside diameter value of the corresponding end working portion actually measured by the post-process measuring device. With the adjusted operating angle, the working operation is continued until the above-indicated other reference value is reached, namely, until the actually measured outside diameter values of the two end working portions have become equal to the respective reference values.
In the second mode of control of the machine, two reference values are set for each end working portion. These two reference values correspond to intermediate and nominal (final) outside diameters of the end working portion. The intermediate outside diameter is larger than the nominal or final outside diameter. The operating angle of the array of working tools is adjusted when the reference value corresponding to the intermediate outside diameter of one of the two end working portions is reached. This adjustment is made based on a difference to the reference value corresponding to the intermediate outside diameter of the other end working portion. With the adjusted operating angle, the working operation is continued to finish the working portions, until the reference value corresponding to the nominal outside diameter of one of the two end working portions is first reached, or until the two reference values corresponding to the nominal outside diameters of the two end working portions are both reached, one after the other.
In one form of the apparatus according to the above third aspect of the invention, the determining means includes: diameter adjusting means for adjusting the diameter values of the two end working portions of the workpiece measured by the post-process measuring device, on the basis of the diameter values of all of the plurality of working portions measured by the post-process measuring device; data obtaining means for obtaining dimensional error data relating to a dimensional error of each of the two end working portions, on the basis of the diameter values of the two end working portions adjusted by the diameter adjusting means; and means for determining the two compensating values for adjusting the two reference values, on the basis of the dimensional error data.
The term xe2x80x9cdimensional error dataxe2x80x9d is interpreted to cover not only the data indicative of the dimensional error per se of the end working portions, but also data indicative of a tendency of change in the dimensional error, and even data indicative of a tendency of change in the tendency of change in the dimensional error.
In an alternative form of the apparatus according to the same third aspect of the invention, the determining means includes: data obtaining means for obtaining dimensional error data relating to a dimensional error of each of the plurality of working portions, on the basis of the diameter values of the plurality of working portions measured by the post-process measuring device; data adjusting means for adjusting the dimensional error data on the two end working portions, on the basis of the dimensional error data on all of the plurality of working portions; and means for determining the two compensating values for adjusting the two reference values, on the basis of the adjusted dimensional error data of the two end working portions.
In another alternative form of the apparatus according to the third aspect of the invention, the determining means includes: data obtaining means for obtaining dimensional error data relating to a dimensional error of each of the plurality of working portions, on the basis of the diameter values of the plurality of working portions measured by the post-process measuring device; provisional value determining means for determining provisional compensating values corresponding to the plurality of working portions, respectively, on the basis of the dimensional error data on all of the plurality of working portions; and means for adjusting the provisional compensating values corresponding to the two end working portions, to obtain respective final compensating values as the two compensating values to be applied to the machine control means, on the basis of the provisional compensating values corresponding to all of the plurality of working portions.
The above second object may also be achieved also according to the third aspect of the present invention, which provides a method of processing a plurality of workpieces by a working system including (a) a working machine for successively processing the plurality of workpieces one after another, each of the workpieces having a plurality of working portions in the form of a plurality of coaxial outer cylindrical surfaces arranged in an axial direction thereof, the working machine including an array of working tools which correspond to the plurality of working portions, respectively, the array of working tools being moved relative to each workpiece to simultaneously process the working portions, (b) an in-process measuring device having two in-process measuring heads for measuring diameter values of respective two end working portions of the plurality of working portions, during a working operation of the machine on each workpiece, the two end working portions being located near opposite axial ends of each workpiece, (c) a post-process measuring device for measuring diameter values of the plurality of working portions, respectively, after each workpiece is processed by the machine, and (d) machine control means for controlling the machine such that an operating angle of the array of working tools relative to each workpiece is adjusted and the working operation of the machine on each workpiece is terminated, on the basis of the diameter values of the two end working portions measured by the in-process measuring heads, in relation to two reference values set for the two end working portions, respectively, the method comprising the steps of: (i) determining two compensating values for adjusting the two reference values, on the basis of the diameter values of all of the plurality of working portions of each workpiece measured by the post-process measuring device; and (ii) applying the two compensating values to the machine control means.
The first object may also be achieved according to a fourth aspect of this invention, which provides a feedback compensating apparatus for a working system including (a) working machine for performing a working operation on each of at least one working portion of each of a plurality of workpieces of at least one kind, to process each working portion as desired, such that working operations on the plurality of workpieces take place successively one after another, (b) machine control means for determining a working condition of the machine on the basis of an extraneous signal, and controlling the machine according to the determined working condition, and (c) a post-process measuring device for measuring actual dimensions of the working portions of the workpieces processed by the machine, the feedback compensating apparatus being connected to the machine control means and the post-process measuring machine, the apparatus comprising: (i) dimensional data obtaining means for obtaining a set of dimensional error data relating to a dimensional error of the processed working portions of the workpieces, for each of the at least one kind of the workpieces, on the basis of outputs of the post-process measuring device; (ii) number data obtaining means for obtaining the number of pre-measured workpieces of each of the at least one kind which have been processed by the machine and which have not been measured by the post-process measuring device; and (iii) compensating means for determining as the extraneous signal a compensating value for each kind of the workpieces, on the basis of the set of dimensional error data and the number of the pre-measured workpieces of the corresponding kind which have been obtained by the dimensional data obtaining means and the number data obtaining means, respectively, the compensating means applying the compensating value to the machine control means, to adjust the working condition of the machine for the workpieces of each kind to be subsequently processed.
In the present feedback compensating apparatus according the fourth aspect of the invention described above, the compensating value for each kind of the workpieces to be applied to the machine control means is determined based on not only the dimensional error data actually obtained for the corresponding kind of the workpieces by the dimensional data obtaining means from the outputs of the post-process measuring device, but also the number of the pre-measured workpieces of the same kind obtained by the number data obtaining means. Since the number of the pre-measured workpieces is taken into account in determining the compensating value, the accuracy of adjustment of the working condition for each kind of the workpieces is improved even when the number of the pre-measured workpieces varies from time to time during continuous operation of the machine on a succession of workpieces.
The apparatus according to the fourth aspect of the invention described above is applicable to the working operations to be performed on successive workpieces of either the same kind or different kinds. Regarding the kind of the workpieces, workpieces whose working portions have the same nominal dimension may be considered to be of different kinds. In this respect, it is desirable in some cases that the workpieces whose working portions have the same nominal dimension be processed in different working conditions of the machine, for example, due to different rigidity values of the workpieces. In this case, the workpieces are considered to be of different kinds.
In one form of the apparatus according to the above fourth aspect of the present invention, the plurality of workpieces are of a single kind, and the compensating means includes memory means for storing a plurality of control rules which correspond to selected respective values of the number of the pre-measured workpieces and which define respective different relationships between the compensating value and the set of dimensional error data for the single kind of workpieces. The memory means also stores a plurality of data groups which correspond to the plurality of control rules and which define relationships between the number of the pre-measured workpieces to be obtained by the number data obtaining means, and an optimum degree of influence of the control rules to be given on the compensating value to be determined. In operation, the compensating means determines the optimum degree of influence of each of the control rules, which optimum degree corresponds to the number of the pre-measured workpieces obtained by the number data obtaining means. Finally, the compensating means determines the compensating value based on the determined optimum degree of influence, the plurality of control rules and the dimensional error data.
In another form of the apparatus according to the fourth aspect of the invention, the compensating means includes memory means for storing a plurality of control rules which correspond to respective combinations of the number of the pre-measured workpieces and the number of the at least one kind of the workpieces and each of which define a relationship between the dimensional error data and the compensating value. In operation, the compensating means selects one of the control rules, depending upon the number of the pre-measured workpieces obtained by the number data obtaining means and the kind of the workpieces, and determining the compensating value on the basis of the selected control rule.
In a further form of the apparatus according to the fourth aspect of the invention, the compensating means includes memory means for storing one control rule for each of the at least one kind of the workpiece, which control rule defines a relationship between the dimensional error data and the compensating value. The memory means also stores data which define a relationship between the number of the pre-measured workpieces and a compensating coefficient used to determine the compensating value. In operation, the compensating means first determines a provisional compensating value on the basis of the dimensional error data obtained by the dimensional data obtaining means, and according to the control rule corresponding to the kind of the workpieces. Then, the compensating means determines the compensating coefficient which corresponds to the number of the pre-measured workpieces obtained by the number data obtaining means. Finally, the compensating means determines a final compensating value to be applied to the machine control means, on the basis of the determined provisional compensating value and the compensating coefficient.
In a still further form of the apparatus according to the fourth aspect of the invention, the compensating means includes memory means for storing a control rule for each of the at least one kind of the workpiece, which control rule defines a relationship among the number of the pre-measured workpieces, the dimensional error data and the compensating value. In operation, the compensating means determines the compensating value, on the basis of the number of the pre-measured workpieces obtained by the number data obtaining means and the dimensional error data obtained by the dimensional data obtaining means, and according to the control rule corresponding to the kind of the workpieces.
The above second object may also be achieved also according to the fourth aspect of the invention, which provides a method of processing a plurality of workpieces by a working system including (a) a working machine for performing a working operation on each of at least one working portion of each of the workpieces of at least one kind, to process each working portion as desired, such that working operations on the plurality of workpieces take place successively one after another, (b) machine control means for determining a working condition of the machine on the basis of an extraneous signal, and controlling the machine according to the determined working condition, and (c) a post-process measuring device for measuring actual dimensions of the working portions of the workpieces processed by the machine, the method comprising the steps of: (i) obtaining a set of dimensional error data relating to a dimensional error of the processed working portions of the workpieces, for each of the at least one kind of the workpieces, on the basis of outputs of the post-process measuring device; (ii) obtaining the number of pre-measured workpieces of each of the at least one kind which have been processed by the machine and which have not been measured by the post-process measuring device; (iii) determining as the extraneous signal a compensating value for each kind of the workpieces, on the basis of the set of dimensional error data and the number of the pre-measured workpieces of the corresponding kind which have been obtained by the dimensional data obtaining means and the number data obtaining means, respectively; and (iv) applying the compensating value to the machine control means, to adjust the working condition of the machine for the workpieces of each kind to be subsequently processed.
The first object may also be achieved according to a fifth aspect of the present invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for successively processing a plurality of workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, the working system being adapted to permit existence between the machine and the measuring device, of at least one pre-measured workpiece which has been processed by the machine and which has not been measured by the measuring device, the feedback compensating apparatus being used with the machine control means and the measuring device, the apparatus comprising: (i) determining means for determining as the extraneous signal a compensating value for adjusting the working condition of the machine for the workpieces to be processed subsequently by the machine, on the basis of the actual dimensions of the working portions of the workpieces which have been measured by the measuring device, the determining means updating the compensating value from time to time on an intermittent basis while the workpieces processed by the machine are measured successively by the measuring device; and (ii) applying means for applying the compensating value to the machine control means.
In the feedback compensating apparatus according to the fifth aspect of this invention described above, the actual dimensions of the working portions of the processed workpieces are successively measured one after another, while the compensating value is determined from time to time on an intermittent basis, and is not determined upon measurement of each processed workpiece. Therefore, the compensating value is not updated in synchronization of the measurement of the processed workpieces.
Since there are some pre-measured workpieces between the machine and the measuring device, there is a measurement delay corresponding to the number of the pre-measured workpieces. Accordingly, updating the compensating value within a period corresponding the measurement delay is meaningless, because an influence of the presently determined or updated compensating value on the measured dimensions of the processed workpieces will not appear until the first workpiece influenced by the compensating value has reached the measuring device and been measured by the measuring device. In view of this fact, the present compensating apparatus determines or updates the compensating value on an intermittent basis as described below in more detail. The present arrangement is effective to reduce the work load of the apparatus, since the frequency of determination of the compensating value is considerably reduced as compared with that where the compensating value is updated when each processed workpiece is measured.
The determining means may be arranged to determine the compensating values based on only dimensional error values which are differences between the actually measured dimensions of the workpieces and the nominal dimension. Alternatively, the determining means may be designed to determine the compensating value based on a variable indicative of a tendency of change in the dimensional error, as well as the dimensional error per se. Further, the determining means may also use a variable indicative of a tendency of change in the variable indicative of the tendency of change in the dimensional error.
In one form of the apparatus according to the fifth aspect of this invention described above, the determining means updates the compensating value from a last value to a present value, and determines the present value only after a first one of the workpieces processed by the machine under the working condition adjusted by the last value has been measured by the measuring device.
In the presence of some number of the pre-measured workpieces between the machine and the measuring device, it is desirable that the present compensating value to be determined reflects more or less an influence of the last compensating value. To this end, it is necessary to determine the present compensating value, namely, to update the compensating value, at a moment not earlier than the moment when the first workpiece influenced by the last compensating value has been measured by the measuring device. In this respect, the above form of the invention is adapted such that the present compensating value is not determined until the first workpiece influenced by the last compensating value has been measured. Thus, the apparatus updates the compensating value on an intermittent basis, with a time interval between adjacent occurrences of determination of the compensating value. This is effective to reduce the work load of the feedback compensating apparatus.
According to another form of the apparatus according to the same fifth aspect of the invention, the determining means includes memory means for storing measured values of the actual dimensions of the processed workpieces obtained by the measuring device, and determines a present value of the compensating value on the basis of a predetermined number of the measured values stored in the memory means, when the number of the stored measured values has become equal to the predetermined number. The determining means clears the memory means and resuming an operation to store therein the measured values obtained by the measuring device, after completion of determination of the present value.
In the light of an unavoidable error in the measurement of each processed workpiece, it is desirable to use not only the present output value of the measuring device, but also some preceding output values of the measuring device, in order to assure improved adequacy of determination of the compensating value. To this end, the above form of the apparatus is adapted to store measured values of the workpieces one after another, so that the present compensating value is determined on the basis of a predetermined number of the stored measured values. Thus, the compensating value is updated each time the predetermined number of the measured values are stored in the memory means. Thus, the compensating value is updated intermittently based on successively measured and stored values of the dimensions of the processed workpieces, irrespective of the number of the pre-measured workpieces. This arrangement also reduces the work load of the compensating apparatus.
The above second object may also be achieved also according to the fifth aspect of this invention, which provides a method of processing a plurality of workpieces by a working system including (a) a working machine for successively processing the workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, such that between the machine and the measuring device, there exist a predetermined number of pre-measured workpieces which have been processed by the machine and which have not been measured by the measuring device, the method comprising the steps of: (i) determining as the extraneous signal a compensating value for adjusting the working condition of the machine for the workpieces to be processed subsequently by the machine, on the basis of the actual dimensions of the working portions of the workpieces which have been measured by the measuring device, the determining means updating the compensating value from time to time on an intermittent basis while the workpieces processed by the machine are measured successively by the measuring device; and (ii) applying the compensating value to the machine control means.
The above first object may also be achieved according to a sixth aspect of this invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for successively processing the workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, the feedback compensating apparatus being used with the machine control means and the measuring device, the apparatus comprising: (i) determining means for determining as the extraneous signal a compensating value for adjusting the working condition of the machine for the workpieces to be processed subsequently by the machine, on the basis of the actual dimensions of the working portion of the workpieces which have been measured by the measuring device, and according to a compensation rule which changes with a change in a vibration level of measured values of the actual dimensions obtained by the measuring device; and (ii) applying means for applying the compensating value to the machine control means.
For instance, the compensating rule is changed so that the compensating value to be determined according to the compensating rule is relatively less responsive to a change in the dimensional error of the processed workpieces when the vibration level is relatively high, while on the other hand the compensating value to be determined is relatively highly responsive to the change in the dimensional error when the vibration level is relatively low. Thus, the present arrangement assures adequate determination of the compensating value so as to reduce the dimensional error of the processed workpieces even when the measured values of the workpieces vibrate to a considerable extent due to vibration of the machine.
The determining means described above may be arranged to determine the compensating values based on only dimensional error values which are differences between the actually measured dimensions of the workpieces and the nominal dimension. Alternatively, the determining means may be designed to determine the compensating value based on a variable indicative of a tendency of change in the dimensional error, as well as the dimensional error per se. Further, the determining means may also use a variable indicative of a tendency of change in the variable indicative of the tendency of change in the dimensional error.
The above second object may also be achieved also according to the sixth aspect of the invention, which provides a method of processing a plurality of workpieces by a working system including (a) a working machine for successively processing the workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, the method comprising the steps of: (i) determining as the extraneous signal a compensating value for adjusting the working condition of the machine for the workpieces to be processed subsequently by the machine, on the basis of the actual dimensions of the working portion of the workpieces which have been measured by the measuring device, and according to a compensation rule which changes with a change in a vibration level of measured values of the actual dimensions obtained by the measuring device; and (ii) applying the compensating value to the machine control means.
The above first object may also be achieved according to a seventh aspect of the present invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for performing a working operation on each of at least one working portion of each of a plurality of workpieces, to process the each working portion as desired, such that working operations on the plurality of the workpieces take place successively one after another, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of the working portions of the workpieces processed or under processing by the working machine, the feedback compensating apparatus being used with the machine control means and the measuring device, the apparatus comprising: (i) data obtaining means for obtaining dimensional data on the basis of outputs of the measuring device during at least one of a first period and a second period following the first period, the working operation on the each working portion being performed during the first period, the dimensional data including a dimensional error of the processed working portions of the workpieces; and (ii) compensating means for determining a compensating value as the extraneous signal on the basis of the dimensional data, and effecting the adjustment of the working condition of the working machine according to the determined compensating value when the compensating value is outside a predetermined tolerable range, the compensating means inhibiting the adjustment of the working condition according to the compensating value when the compensating value falls within the tolerable range.
In the feedback compensating apparatus according to the seventh aspect of the invention as described above, the working condition of the machine is not adjusted, i.e., remains unchanged, when the determined compensating value is sufficiently close to zero or within a tolerable range. In other words, the determined compensating value is utilized to adjust the working condition of the machine when the compensating value is outside the tolerable range. This arrangement permits enhanced stability of the dimensional accuracy of the processed workpieces, as compared with an arrangement in which each compensating value determined by the compensating means is actually used to adjust the working condition, irrespective of whether the determined compensating value is sufficiently close to zero.
The inhibition of the adjustment of the working condition of the machine according to the compensating value may be accomplished by zeroing the compensating value to be applied to the machine control means, or by applying to the machine control means a signal which inhibits the adjustment of the working condition according to the compensating value. Alternatively, the adjustment of the working condition may be inhibited by inhibiting the application of the compensating value to the machine control means.
The above second object may also be achieved also according to the above seventh aspect of this invention, which provides a method of processing at least one working portion provided on each of a plurality of workpieces such that the workpieces are successively processed one after another by a working machine, comprising the steps of: (i) obtaining dimensional data including a dimensional error of the working portions of the workpieces, during at least one of a first period and a second period following the first period, the working operation on the each working portion being performed during the first period; (ii) determining a compensating value as the extraneous signal on the basis of the dimensional data; and (iii) adjusting the working condition of the working machine according to the compensating value when the compensating value is outside a predetermined tolerable range, and inhibiting the adjustment of the working condition according to the compensating value when the compensating value falls within the tolerable range.
The above first object may also be achieved according to the eighth aspect of this invention, which provides a feedback compensating apparatus for a working system including (a) a working machine for successively processing the workpieces, (b) machine control means for determining a working condition of the working machine on the basis of an extraneous signal, and controlling the working machine according to the determined working condition, and (c) a measuring device for measuring actual dimensions of working portions of the workpieces processed by the working machine, the feedback compensating apparatus being used with the machine control means and the measuring device, the apparatus comprising: (i) manual compensating means for effecting an manual adjustment of the working condition of the machine, the manual compensating means determining as the extraneous signal a manual compensating value to adjust the working condition of the machine, in response to manual compensating data entered by an operator of the machine, the manual compensating means applying the manual compensating value to the machine control means; and (ii) automatic compensating means for effecting an automatic adjustment of the working condition, the automatic compensating means determining also as the extraneous signal an automatic compensating value for adjusting the working condition of the machine for the workpieces to be processed subsequently by the machine, on the basis of the actual dimensions of the working portion of the workpieces which have been measured by the measuring device, the automatic compensating means applying the automatic compensating value to the machine control means. The automatic compensating means interrupting an operation to effect the automatic adjustment when the manual adjustment by the manual compensating means is started, and resuming the operation to effect the automatic adjustment, at a moment not earlier than a moment when a first one of the workpieces processed by the machine under the working condition adjusted by the manual compensating value has been measured by the measuring device.
In the present apparatus according to the eighth aspect of this invention as described above, the working condition of the machine is adjusted by the machine control means, according to the manual compensating value received from the manual compensating means, or the automatic compensating value received from the automatic compensating means. When the manual adjustment according to the manual compensating value is started, the operation of the automatic compensating means is interrupted, until the first workpiece processed under the working condition adjusted by the manual compensating value has been measured by the measuring device. That is, the operation to effect the automatic adjustment of the working condition is resumed when or after the first workpiece influenced by the manual adjustment has been measured. Thus, the manual adjustment of the working condition is predominant over the automatic adjustment, and the automatic compensating value is determined on the basis of the measured dimensions of the workpieces processed under the influence of the manual compensating value.
Where there are some pre-measured workpieces which have been processed but have not been measured, the dimensions of these workpieces measured after the manual adjustment is started does not reflect an influence of the manual compensating value, and the use of these dimensions to determine the automatic compensating value is meaningless. Accordingly, the automatic compensating value is determined only after the first workpiece influenced by the manual compensating value has been measured and is available to determine the automatic compensating value. Thus, the present apparatus assures high accuracy of automatic adjustment of the working condition of the machine even after the manual adjustment.
The manual compensating data may be directly entered into the machine control means, or indirectly through the automatic compensating means.
The interruption of the operation to effect the automatic adjustment of the working condition of the machine is interpreted to cover at least inhibiting the application of the determined automatic compensating value to the machine control means. Namely, the operation of the automatic compensating means may be stopped after the automatic compensating means is determined but before the determined automatic compensating value is supplied to the machine control means.
The term xe2x80x9cresuming the operation to effect the automatic adjustmentxe2x80x9d is interpreted to mean that actions of the automatic compensating means to determine the automatic compensating value and apply it to the machine control means are both resumed where the xe2x80x9cinterruptionxe2x80x9d is effected with respect to these actions, or mean that an action to apply the determined automatic compensating value to the machine control means is resumed where the xe2x80x9cinterruptionxe2x80x9d is effected with respect to this action only.
Where there are any pre-measured workpieces between the machine and the measuring device, the first workpiece processed under the influence of the manual compensating value is not measured immediately after the manual compensating value is applied to the machine control means. In this sense, the moment at which the operation of the automatic compensating means is resumed is determined to be a moment not earlier than the moment at which the above-indicated first workpiece has been measured. The term xe2x80x9cnot earlier thanxe2x80x9d means that the operation of the automatic compensating means may be resumed when two or more workpieces processed under the influence of the manual compensating values have been measured.
In one form of the apparatus according to the eighth aspect of the invention, the automatic compensating means includes memory means for storing the dimensions of the processed workpieces which are successively measured by the measuring device. The automatic compensating means determines the automatic compensating value on the basis of the dimension of the workpiece measured last by the measuring device, and at least one dimension previously measured and stored in the memory means. The automatic compensating means resumes the operation to effect the automatic adjustment by storing the dimensions to be subsequently measured with the memory means cleared, at the moment not earlier than the moment when the first workpiece influenced by the manual compensating value has been measured.
The phrase xe2x80x9cdetermines the automatic compensating value on the basis of the dimension of the workpiece measured last by the measuring device, and at least one dimension previously measured and stored in the memory meansxe2x80x9d may be interpreted to cover: (1) a case in which the automatic compensating value is determined based on a dimensional error which is a difference between the measured dimension and a nominal dimension of the workpiece, and a tendency of change in this dimensional error; (2) a case in which the automatic compensating value is determined based on each measured dimension, a tendency of change in the measured dimension, and a tendency of change in the tendency of change in the measured dimension; and (3) a case in which the automatic compensating value is determined based on each measured dimension as adjusted by the previously measured dimension or dimensions. The tendency of change in the dimensional error may be represented by a first time derivative of the dimensional error, and the tendency of change in the tendency of change in the measured dimension may be represented by a second time derivative of the measured dimension.